Temperature and humidity sensor SHT25
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SENSIRION THG SENSOR COMPANY Datasheet SHT25 Humidity and Temprature Sensor IC ■ Fully calibrated with 1.8%RH accuracy ■ Digital output, I2C interface ■ Low power consumption ■ Excellent long term stability ■ DFN type package - reflow solderable Product Summary SHT25, the new humidity and temperature sensor of Sensirion is about to set new standards in terms of size and intelligence: Embedded in a reflow solderable Dual Flat No leads (DFN) package of 3 x 3mm foot print and 1.1mm height it provides calibrated, linearized signals in digital, I2C format. With a completely new designed CMOSens® chip, a reworked capacitive type humidity sensor and an improved band gap temperature sensor the performance has been lifted even beyond the outstanding level of the previous sensor generation (SHT1x and SHT7x). For example, measures have been taken to stabilize the behavior at high humidity levels. Every sensor is individually calibrated and tested. Lot identification is printed on the sensor and an electronic identification code is stored on the chip - which can be read out by command. Furthermore, the resolution of SHT25 can be changed by command (8/12bit up to 12/14bit for RH/T), low battery can be detected and a checksum helps to improve communication reliability. With made improvements and the miniaturization of the sensor the performance-to-price ratio has been improved - and eventually, any device should benefit from the cutting edge energy saving operation mode. For testing SHT25 a new evaluation Kit EK-H4 is available. Dimensions Sensor Chip 3.0 0 SHT25 features a generation 4C CMOSens® chip. Besides the capacitive relative humidity sensor and the band gap temperature sensor, the chip contains an amplifier, A/D converter, OTP memory and a digital processing unit. Material Contents While the sensor itself is made of Silicon the sensors' housing consists of a plated Cu lead-frame and green epoxy-based mold compound. The device is fully RoHS and WEEE compliant, e.g. free of Pb, Cd and Hg. 0.8 typ 2.2 FF 2 Bottom View >| | ^ 0.4 03, NC VDD SCL u u u 4 5 2.4 Additional Information and Evaluation Kits Additional information such as Application Notes is available from the web page www.sensirion.com/sht25. For more information please contact Sensirion via info@sensirion.com. For SHT25 two Evaluation Kits are available: EK-H4, a four-channel device with Viewer Software, that also serves for data-logging, and a simple EK-H5 directly connecting one sensor via USB port to a computer. n n n n n n NC VSS SDA Figure 1: Drawing of SHT25 sensor package, dimensions are given in mm (1mm = 0.039inch), tolerances are ±0.1mm. The die pad (center pad) is internally connected to VSS. The NC pads must be left floating. VSS = GND, SDA = DATA. Numbering of E/O pads starts at lower right corner (indicated by notch in die pad) and goes clockwise (compare Table 2). www.sensirion.com Version 2 - December 2011 1/14

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Datasheet SHT25 2 Application Information 2.1 Soldering Instructions The DFN's die pad (centre pad) and perimeter I/O pads are fabricated from a planar copper lead-frame by over-molding leaving the die pad and I/O pads exposed for mechanical and electrical connection. Both the I/O pads and die pad should be soldered to the PCB. In order to prevent oxidation and optimize soldering, the bottom side of the sensor pads is plated with Ni/Pd/Au. On the PCB the I/O lands8 should be 0.2mm longer than the package I/O pads. Inward corners may be rounded to match the I/O pad shape. The I/O land width...

Datasheet SHT25 5EN5IRION recommended to further process the sensors within 1 year after date of delivery. It is of great importance to understand that a humidity sensor is not a normal electronic component and needs to be handled with care. Chemical vapors at high concentration in combination with long exposure times may offset the sensor reading. For this reason it is recommended to store the sensors in original packaging including the sealed ESD bag at following conditions: Temperature shall be in the range of 10°C - 50°C and humidity at 20 - 60%RH (sensors that are not stored in ESD...

Datasheet SHT25 3 Interface Specifications of MCUs. See Table 4 and Table 5 for detailed I/O characteristic of the sensor. 4 Electrical Characteristics 4.1 Absolute Maximum Ratings The electrical characteristics of SHT2x are defined in Table 1. The absolute maximum ratings as given in Table 3 are stress ratings only and give additional information. Functional operation of the device at these conditions is not implied. Exposure to absolute maximum rating conditions for extended periods may affect the sensor reliability (e.g. hot carrier degradation, oxide breakdown). Pin Name Comment 1 SDA...

Datasheet SHT25 1/fsCL power-up, the sensor needs at most 15ms, while SCL is high, for reaching idle state, i.e. to be ready accepting commands from the master (MCU). Current consumption during start up is 350mA maximum. Whenever the sensor is powered up, but not performing a measurement or communicating, it is automatically in idle state (sleep mode). 5.2 Start / Stop Sequence Each transmission sequence begins with Start condition (S) and ends with Stop condition (P) as displayed in Figure 13 and Figure 14. tsCLH tSCLL tR tF 70% 30% SCL SDA valid write tsu tHD 70% 30% SDA SDA valid read...